This invention relates generally to an air conditioning system for automobiles, and more particularly, to an automatic control system for such an air conditioner based on a dynamic model of the system.
Various types of air conditioning systems have been used and applied for automobiles so as to control the temperature, humidity, cleanness and so on of the air within a vehicle compartment. Among such various types, an air conditioning apparatus which controls only the temperature is widely used. In such air conditioning apparatus for automobiles, in order to control the air temperature at air outlets throughout a wide range from a low temperature to a high temperature, air sent in the apparatus is once cooled by a cooler, such as an evaporator, and then the cooled air is heated by a heater, such as a heater core, so as to obtain a desired temperature of the blowing air. This series of apparatus for blowing, cooling and heating air is referred to as blowing air control measure, and the entire system is referred to as an air conditioning unit. As such air conditioning unit widely used in these days as an air conditioner of automobiles there are two types, one being a reheat type which is arranged to change the calorific value supplied to a heater, and the other being air-mixing type which is arranged to change the ratio of air passing through the heater.
In either of these two types, the temperature of air within a vehicle compartment is controlled by the calorific value of blow off air, i.e. the flow rate and temperature of the blow off air. The flow rate of the blow off air is determined by the blowing capability of a blower motor or the like as used in the system, and the temperature thereof is determined by the cooling capability of the cooler (evaporator). That is, the capability of the cooling system including a compressor and heating capability of a heater, namely, the amount of circulated hot water in the case of reheat type and the damper opening degree of the air-mixing damper in the case of air-mixing type.
When an air conditioning unit starts operating, the temperature of air within a vehicle compartment is detected to feedback control the temperature and flow rate of blow off air on the basis of the difference between the detected temperature and a predetermined target temperature. As a result, the temperature of air within the vehicle compartment, which will be referred to as internal air temperature hereinafter, approaches the setting target temperature gradually, because of the calorific value of the blow off air.
Such a control of air temperature is disclosed in Japanse Patent Provisional Publications Nos. 55-47914 and 55-77659.
The above-described conventional apparatus is based on feedback control which is performed on th basis of the deviation of a detected internal air temperature from a setting target temperature so that the former approaches the latter, and some conventional apparatus further adopts prediction control in which the amount of control is determined so that predetermined conditions of thermal equilibrium are satisfied considering the external air temperature and solar radiation amount. Furthermore, the amount of air to be blown off is just simply controlled such that the blow off air amount is increased when the above-mentioned deviation, that is the difference between the above-mentioned temperatures is large and to decrease the same as the difference becomes smaller.
Therefore, transient response at the time of the change of the setting value of the target temperature is not necessarily satisfactory, such that the transient response is poor depending on the internal air temperature at such instant, the capability of the air conditioning unit, and therefore, there have been a problem that it is difficult to provide comfortable environment to vehicle occupants. Furthermore, when environmental conditions, such as solar radiation, of the system where air conditioning is performed are changed, conventional control is apt to deviate from thermal equilibrium state and therefore, it takes a relatively long period of time until the internal air temperature is stably set at a target temperature. In other words, conventional control apparatus are not necessararily optimal when environmental condition varies.
While the capability of an air conditioning unit is determined by the combination of blow off air amount, cooling capability of the cooler, heating capability of the heater and so on, it has not been made clear as to what combination of these factors provides an optimal control. Therefore, these factors have hitherto been combined simply by the experiences of designers as the above-mentioned control of blow off air amount. Accordingly, it cannot be said that the capability of air conditioning unit has hitherto been derived sufficiently.
The present invention has been made so as to resolve such problems, and contemplates to provide an air conditioner for automobiles, which controls the temperature (internal air temperature) within vehicle compartment deriving fully the capability of a used air conditioning unit.
Moreover, when an air conditioner for automobile is arranged so that respective air discharge outlets can be independently controlled, it is desired that temperatures at a plurality of different places within a vehicle compartment can be controlled to be respectively equal to setting target tempeatures which are predetermined individually. In detail, while some air conditioners of recent motor vehicles are capable of controlling temperatures at given different positions within the vehicle compartment, such as front seat and rear seat, left seat and right seat, or upper portion and lower portion, by way of a so called dual-air conditioner having two air conditioning units at the front and rear portions of the vehicle compartment, or by way of an air conditioner which is capable of controlling airflow rate and temperature of air at respective discharge outlets from which air conditioned air is discharged into the vehicle compartment, the response in temperature control is poor, and a plurality of airflows from different discharge outlets interfere with each other so that it is very difficult to provide desired internal air temperatures at each of the given positions.
The present invention contemplates to provide an air conditioner which is capable of controlling temperatures at a plurality of positions within a vehicle compartment with high response so that desired temperatures can be provided.